I got UT 2K4 and was able to play it fine for about 3 hours, then it crashed. I got this from the Event Viewer:

The computer has rebooted from a bugcheck. The bugcheck was: 0x10000050 (0x80e0a6a8, 0x00000000, 0xbfa71e65, 0x00000000). A dump was saved in: C:\WINDOWS\Minidump\Mini040304-01.dmp.
I have absolutely no idea what could've caused this, though I think it might've been my sound driver because I could still hear the sounds even after the game crashed, or my machine might've overheated because it runs at about 52-54º C normally, and can't imagine how hot UT must make it.